A reclining device including: a lower frame member that configures a portion of a frame of a vehicle seat; an upper frame member that configures a portion of the frame of the vehicle seat; a recliner that is provided between and welded to both the lower frame member and the upper frame member, and that couples the upper frame member to the lower frame member such that a relative rotation angle of the upper frame member is adjustable relative to the lower frame member; a lower side engagement portion that is provided at the lower frame member and that is formed in a circular arc shape that is concentric with the recliner; and an extension member that extends from the upper frame member toward a lower frame member side.